Transcript for 2-Star General Killed in Afghanistan Academy and the Heroes That Saved Lives

An American, a two-star general killed by an Afghan soldier. It's believed the U.S. Might have trained him. Tonight that U.S. Base the scene of the shooting on lockdown. This evening, what we're learning about the so-called guardian angels there in that room the moment the gunman opened fire and what they did that likely saved lives. Martha Raddatz has been reporting on this story all day for us with new details here tonight. Reporter: It was broad daylight -- at a training center. Inside, major general Harold Greene, the deputy commander of the training mission, was meeting with the troops, Americans, Afghans and other N.A.T.O. Forces. Then from an elevated position the gunman strikes. He is a member of the Afghan security forces, trained by Americans, in uniform opening fire with an automatic weapon hitting the general and those around him. More than a dozen wounded many seriously. Within seconds, the so-called "Guardian angels" soldiers, Americans armed and present to protect against such attacks fire back killing the gun. But it's too late. Greene, the American two-star general, one of the nation's top ranking officers, was dead. The loss of any life is tragic. The symbolism will have a huge effect on U.S. Forces. Reporter: Major general Greene who lived in Virginia and is well known in the military has a son in the army and a daughter who recently graduated from college. He is the first general officer to die in a war zone from hostile fire since Vietnam. American soldiers pride themselves on taking care of their leaders. The many generals I have traveled with in Afghanistan are always surrounded by security but that failed today. The number of these attacks has gone down as American forces wind down their war in Afghanistan, but it is still a dangerous place, and losing a general who had mentored so many troops with more than 30 years in the military is an especially painful reminder. Extraordinary headline when we heard it today. Thank you.

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